US20220321021A1 - Power converter and electric motor braking method - Google Patents
Power converter and electric motor braking method Download PDFInfo
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- US20220321021A1 US20220321021A1 US17/310,302 US201917310302A US2022321021A1 US 20220321021 A1 US20220321021 A1 US 20220321021A1 US 201917310302 A US201917310302 A US 201917310302A US 2022321021 A1 US2022321021 A1 US 2022321021A1
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- 238000000034 method Methods 0.000 title claims description 14
- 239000003990 capacitor Substances 0.000 claims abstract description 39
- 238000009499 grossing Methods 0.000 claims abstract description 31
- 230000001172 regenerating effect Effects 0.000 claims abstract description 24
- 239000004065 semiconductor Substances 0.000 claims abstract description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000007935 neutral effect Effects 0.000 description 3
- 230000008929 regeneration Effects 0.000 description 2
- 238000011069 regeneration method Methods 0.000 description 2
- 230000003247 decreasing effect Effects 0.000 description 1
- 238000001514 detection method Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000006698 induction Effects 0.000 description 1
- 230000010354 integration Effects 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
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Classifications
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M5/00—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases
- H02M5/40—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc
- H02M5/42—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters
- H02M5/44—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac
- H02M5/453—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal
- H02M5/458—Conversion of ac power input into ac power output, e.g. for change of voltage, for change of frequency, for change of number of phases with intermediate conversion into dc by static converters using discharge tubes or semiconductor devices to convert the intermediate dc into ac using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/0003—Details of control, feedback or regulation circuits
- H02M1/0009—Devices or circuits for detecting current in a converter
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
- H02M7/42—Conversion of dc power input into ac power output without possibility of reversal
- H02M7/44—Conversion of dc power input into ac power output without possibility of reversal by static converters
- H02M7/48—Conversion of dc power input into ac power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
- H02M7/483—Converters with outputs that each can have more than two voltages levels
- H02M7/49—Combination of the output voltage waveforms of a plurality of converters
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/06—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
- H02P3/18—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor
-
- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02P—CONTROL OR REGULATION OF ELECTRIC MOTORS, ELECTRIC GENERATORS OR DYNAMO-ELECTRIC CONVERTERS; CONTROLLING TRANSFORMERS, REACTORS OR CHOKE COILS
- H02P3/00—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters
- H02P3/06—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter
- H02P3/18—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor
- H02P3/22—Arrangements for stopping or slowing electric motors, generators, or dynamo-electric converters for stopping or slowing an individual dynamo-electric motor or dynamo-electric converter for stopping or slowing an ac motor by short-circuit or resistive braking
Definitions
- the present invention relates to a power converter and an electric motor braking method.
- a power converter supplies AC power converted from DC power to an electric motor and drives an electric motor and a mechanical load interlocked with the rotation of the electric motor.
- regenerative energy is generated by an electromotive force.
- a voltage on a DC side (a DC voltage) of the power converter increases. In that case, it may be difficult to quickly stop the electric motor when a discharge circuit is used to avoid the occurrence of an overvoltage state of the DC voltage.
- An object of the present invention is to provide a power converter and an electric motor braking method capable of braking an electric motor more quickly.
- a power converter includes: a diode converter; an inverter; a smoothing capacitor; a resistor; a current sensor; an estimation unit; and a control unit.
- the diode converter rectifies an alternating current from a power supply.
- the inverter is formed such that a DC side is connected to a DC output of the diode converter and an AC side is connected to an electric motor and includes a semiconductor switching element which converts DC power on the DC side into AC power and a reverse connection diode which is connected in antiparallel with the semiconductor switching element.
- the smoothing capacitor is provided in the DC output of the diode converter.
- the resistor is connected in parallel with the smoothing capacitor.
- the current sensor detects a load current flowing between the inverter and the electric motor.
- the estimation unit calculates an estimation value of the DC voltage Vdc on the DC side on the basis of a current value I detected by the current sensor.
- the control unit controls the inverter so that the estimation value of the DC voltage Vdc on the DC side does not exceed a predetermined reference voltage during a period in which the electric motor is in a regenerative state.
- FIG. 1 is a diagram showing an example of a power converter according to a first embodiment.
- FIG. 2 is a diagram showing a cell unit of an embodiment.
- FIG. 3 is a flowchart of a process relating to braking control of an embodiment.
- FIG. 4 is a diagram showing a cell unit according to a second embodiment.
- a “positive electrode P” and a “negative electrode N” are defined first.
- “Positive electrode P” means a portion having a positive potential when a power converter 1 is operated.
- Negative electrode N means a portion having a negative potential when the power converter 1 is operated.
- a reference voltage Vdc 0 of a DC link in the power converter 1 is defined as a predetermined voltage.
- the reference voltage Vdc 0 is, for example, a voltage between the positive electrode P and the negative electrode N.
- the reference voltage Vdc 0 is sometimes called a DC (DC link) rated voltage.
- the power converter 1 converts AC power supplied from an AC power supply 2 into DC power, converts the converted DC power into AC power having a desired frequency and voltage, and supplies the AC power to an electric motor 3 .
- the electric motor 3 is, for example, a three-phase induction motor, but is not limited thereto.
- the power supply side of the power converter 1 is connected to the AC power supply 2 via a circuit breaker 4 .
- the circuit breaker 4 interrupts the power supplied from the AC power supply 2 (the power supply) on the basis of the control of a control device 7 to be described later. Additionally, as shown in FIG. 1 , the circuit breaker 4 may be separated from the power converter 1 or may be a part of the power converter 1 .
- the power converter 1 includes a plurality of cell units 6 s
- the power converter 1 may include a three-phase converter and a three-phase inverter instead of the plurality of cell units 6 s.
- FIG. 1 is a diagram showing an example of the power converter 1 of the embodiment.
- an electric circuit system is indicated by a single line and switches and the like are not shown.
- the power converter 1 includes, for example, an input transformer 5 , a plurality of cell units 6 s , a control device 7 , and a current sensor AM.
- the AC power is supplied from the AC power supply 2 to the input transformer 5 .
- the input transformer 5 transforms the voltage of the AC power supplied from the AC power supply 2 (primary voltage) into a desired secondary voltage and supplies the AC power of the secondary voltage to each of the plurality of cell units 6 s .
- the input transformer 5 includes a primary coil and a plurality of groups of coils (secondary coils) insulated from each other. The primary coil and the secondary coil are also insulated.
- the plurality of cell units 6 s include, for example, three first-phase load cell units 6 A 1 , 6 A 2 , and 6 A 3 (U 1 , U 2 , and U 3 in the drawings), three second-phase load cell units 6 B 1 , 6 B 2 , and 6 B 3 (V 1 , V 2 , and V 3 in the drawings), and three third-phase load cell units 6 C 1 , 6 C 2 , and 6 C 3 (W 1 , W 2 , and W 3 in the drawings).
- the cell units 6 A 1 , 6 A 2 , 6 A 3 , 6 B 1 , 6 B 2 , 6 B 3 , 6 C 1 , 6 C 2 , and 6 C 3 have the same circuit configuration and will be simply referred to as the cell unit 6 when they are described without distinction.
- Each cell unit 6 converts the three-phase AC power supplied from the secondary coil of the input transformer 5 into DC power, converts the converted DC power into AC power having a desired frequency and voltage, and outputs the AC power.
- a first group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 A 1 .
- a second group of the secondary side of the input transformer 5 is connected to the input of the cell unit V 1 .
- a third group of the secondary side of the input transformer 5 is connected to the input of the cell unit W 1 .
- a fourth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 A 2 .
- a fifth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 B 2 .
- a sixth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 C 2 .
- a seventh group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 A 3 .
- An eighth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 B 3 .
- a ninth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6 C 3 .
- the outputs of the cell units 6 A 1 , 6 A 2 , and 6 A 3 are electrically connected in series in the shown order.
- An output terminal of the cell unit 6 A 3 which is not connected to the cell unit 6 A 2 is connected to the first phase (U phase) of the electric motor 3 .
- An output terminal of the cell unit 6 A 1 which is not connected to the cell unit 6 A 2 is connected to a neutral point.
- the outputs of the cell units 6 B 1 , 6 B 2 , and 6 B 3 are electrically connected in series in the shown order.
- An output terminal of the cell unit 6 B 3 which is not connected to the cell unit 6 B 2 is connected to the second phase (V phase) of the electric motor 3 .
- An output terminal of the cell unit 6 B 1 which is not connected to the cell unit 6 B 2 is connected to a neutral point.
- the outputs of the cell units 6 C 1 , 6 B 2 , and 6 B 3 are electrically connected in series in the shown order.
- An output terminal of the cell unit 6 C 3 which is not connected to the cell unit 6 C 2 is connected to the third phase (W phase) of the electric motor 3 .
- An output terminal of the cell unit 6 C 1 which is not connected to the cell unit 6 C 2 is connected to a neutral point. Accordingly, the power converter 1 can supply a large amount of AC power to the electric motor 3 .
- a current sensor AM 1 and a current sensor AM 2 detect a load current (a phase current) flowing between the electric motor 3 and the inverter 13 ( FIG. 2 ) of the power converter 1 .
- the current sensor AM 1 is provided on the first phase of the AC output and the current sensor AM 2 is provided on the third phase of the AC power. Since the second-phase current of the AC output can be obtained from the values of the current sensor AM 1 and the current sensor AM 2 , the second-phase current can be omitted.
- the current sensor AM 1 and the current sensor AM 2 are not distinguished from each other, they may be simply referred to as a current sensor AM.
- a current value detected by the current sensor AM may be referred to as a current I.
- the control device 7 controls or protects each cell unit 6 .
- the control device 7 includes, for example, a storage unit 71 , an operation control unit 72 , an estimation unit 73 , and a braking control unit 74 .
- the storage unit 71 stores a variety of data relating to the control of the plurality of cell units 6 s .
- the variety of data includes, for example, a limit value (a threshold value Vth) for limiting the overvoltage of the DC voltage of the cell unit 6 , a reference voltage Vdc 0 of the DC voltage of the cell unit 6 , history data and integrated value data of a current value I detected by the current sensor AM, an estimation value of a DC voltage value Vdc of the cell unit 6 (hereinafter, referred to as a DC voltage value Vdc_est), and the like.
- the threshold value Vth is defined as, for example, the upper-limit value of the DC voltage of the DC link.
- the reference voltage Vdc 0 is an example of the control target voltage.
- the operation control unit 72 generates a control signal for controlling a switching element 13 S ( FIG. 2 ) included in each cell unit 6 on the basis of data stored in the storage unit 71 , for example, information representing the DC voltage value Vdc_est and information representing the current I detected by the current sensor AM.
- the operation control unit 72 controls each cell unit 6 by sending the generated control signal to each cell unit 6 .
- the operation control unit 72 acquires a signal representing the control state of the electric motor 3 (for example, a feedback signal of a rotation speed) and controls each cell unit 6 on the basis of the feedback signal.
- the control device 7 acquires a control instruction signal of the electric motor 3 from other devices and controls each cell unit 6 on the basis of the control instruction signal.
- the estimation unit 73 calculates the DC voltage value Vdc_est on the basis of the current value I detected by the current sensor AM. The calculation of the DC voltage value Vdc_est will be described below.
- the braking control unit 74 controls each unit to brake the electric motor 3 while adjusting the DC voltage Vdc not to exceed the reference voltage Vdc 0 on the basis of the DC voltage value Vdc_est. For example, the braking control unit 74 opens the circuit breaker 4 at a desired timing associated with the braking control of the electric motor 3 . This desired timing may be matched when the electric motor 3 is in the regenerative state.
- the braking control unit 74 controls the inverter 13 so that more AC power is supplied from the electric motor 3 to the inverter 13 during a period in which the electric motor 3 is in the regenerative state. At that time, the braking control unit 74 adjusts the DC voltage value Vdc_est not to exceed the reference voltage Vdc 0 on the DC side. The control of the circuit breaker 4 and the inverter 13 will be described in detail later.
- FIG. 2 is a diagram showing the cell unit 6 of the embodiment.
- the cell unit 6 includes, for example, a diode converter 12 , an inverter 13 , a smoothing capacitor 14 , resistors 15 and 16 , and a cell unit control unit CUC.
- the DC output of the diode converter 12 and the DC input of the inverter 13 are electrically connected with each other via a DC link between the positive electrodes (P) and between the negative electrodes (N).
- the smoothing capacitor 14 is provided in the DC link and the terminal of the smoothing capacitor 14 is electrically connected to the positive electrode and the negative electrode of the DC link.
- the cell unit 6 A 1 will be illustrated and an example thereof will be described while showing the connection relationship with the outside. The same applies to the other cell units 6 .
- the diode converter 12 is a three-phase AC input type forward converter and the input portion is electrically connected to one group of the secondary side of the input transformer 5 .
- the diode converter 12 converts the AC power input from the input transformer 5 into the DC power by rectifying the alternating current.
- the smoothing capacitor 14 smoothes the converted DC voltage.
- the inverter 13 is a single-phase AC output type inverse converter.
- the inverter 13 includes, for example, the switching element 13 S which converts the DC power on the DC side into the AC power and a reverse connection diode 13 D which is connected in antiparallel with the switching element 13 S.
- the switching element 13 S is an example of the semiconductor switching element.
- the DC side is connected to the DC output of the diode converter 12 and the AC side is connected in series with the output of the electric motor 3 or another cell unit 6 .
- the inverter 13 outputs, for example, the converted AC power to the first phase of the electric motor 3 .
- the resistors 15 and 16 are connected in series with each other and both ends connected in series with each other are connected in parallel to the smoothing capacitor 14 .
- the connection point of the resistors 15 and 16 is connected to the frame of the cell unit 6 .
- the resistors 15 and 16 discharge the electric charge accumulated in the smoothing capacitor 14 .
- the cell unit control unit CUC generates a signal for controlling a switching element constituting the diode converter 12 and the inverter 13 on the basis of a gate pulse signal from the control device 7 .
- the gate pulse signal from the control device 7 is given to the switching element constituting the diode converter 12 and the inverter 13 via the cell unit control unit CUC.
- FIG. 3 is a flowchart of a process associated with the braking control of the embodiment.
- the initial value of the DC voltage value Vdc_est is defined as 0.
- a series of processes shown in the drawing is repeatedly performed at predetermined intervals.
- the braking control unit 74 determines whether or not the DC voltage value Vdc_est exceeds the threshold value Vth (step SA 02 ). Additionally, the DC voltage value Vdc_est is calculated in the previous process cycle.
- the braking control unit 74 turns off the circuit breaker 4 (step SA 04 ) and ends a series of processes in the current cycle.
- the braking control unit 74 operates the inverter 13 without turning off the circuit breaker 4 (step SA 06 ).
- the braking control unit 74 determines whether or not the stop instruction of the inverter 13 from the host device is detected (step SA 08 ). When the stop instruction of the inverter 13 from the host device is not detected, the braking control unit 74 advances the process to step SA 02 .
- the braking control unit 74 stops the output of the inverter 13 (step SA 10 ).
- the braking control unit 74 turns off the circuit breaker 4 (step SA 12 ).
- the estimation unit 73 calculates the DC voltage value Vdc_est using the following formula (1) (step SA 20 ).
- the DC voltage value Vdc_est is defined by the following formula (1).
- Vdc_est Vdc ⁇ 0 ⁇ e - t RC + 1 / C ⁇ ⁇ Ir ⁇ ( t ) ⁇ dt ⁇ ... ( 1 )
- Vdc 0 Reference voltage of DC part
- Ir(t) Regenerative current flowing from electric motor 3 to inverter 13 at time t
- the resistance value becomes the sum of the resistance values of the resistor 15 and the resistor 16 .
- the capacitor C becomes the capacity of the smoothing capacitor 14 . Additionally, when the smoothing capacitor 14 is configured as a combination of capacitors connected in parallel with each other, the capacitor C becomes the sum of the capacities of the plurality of capacitors.
- the first term on the right side of the above-described formula (1) sets the reference voltage Vcd 0 of the DC part as the initial value and defines a discharge characteristic according to a time constant RC defined by the resistance value R of the DC part and the capacitor C of the DC part.
- the second term defines a change in voltage due to the charging of the capacitor C of the DC part charged by the regenerative current Ir(t).
- the right side of formula (2) is the same as the right side of formula (1).
- the braking control unit 74 determines whether or not the DC voltage value Vdc_est derived by the calculation using formula (1) exceeds the predetermined reference voltage Vdc 0 of the DC part (step SA 22 ). This determination corresponds to the determination of whether the condition of formula (2) is satisfied. Accordingly, the braking control unit 74 can indirectly detect the charging state of the smoothing capacitor 14 . Additionally, the integration of the regenerative current Ir(t) may be calculated by using the integrated value of Ir(t) for a predetermined period. For example, the predetermined period may be set to a range that is a natural number multiple of the basic cycle of the AC output of the inverter 13 .
- the braking control unit 74 controls the regenerative current from the electric motor 3 to increase by increasing the instruction value of the inverter 13 (step SA 24 ). Accordingly, the braking control unit 74 can allow more current to flow from the side of the electric motor 3 to the inverter 13 by increasing the DC voltage value Vdc estimated to have a margin until the overvoltage state not to exceed the reference voltage Vdc 0 . Additionally, it is conceived that the instruction value of the inverter 13 is to define the regeneration amount and the regeneration amount increases in accordance with an increase in the instruction value.
- the braking control unit 74 controls the regenerative current from the electric motor 3 to decrease by decreasing the instruction value of the inverter 13 (step SA 26 ). Accordingly, the braking control unit 74 can decrease the current flowing from the side of the electric motor 3 to the inverter 13 to decrease the DC voltage value Vdc estimated to be in the overvoltage state.
- the braking control unit 74 determines whether the speed of the electric motor 3 is zero (step SA 28 ).
- the braking control unit 74 repeats the process from step SA 20 when the speed of the electric motor 3 is not zero.
- the braking control unit 74 ends a series of processes of the current cycle when the speed of the electric motor 3 is zero.
- the speed of the electric motor 3 when the speed becomes lower than the speed defined by the threshold value may be regarded as zero by determining the speed of the electric motor 3 using the threshold value in the vicinity of zero instead of determining whether or not the speed of the electric motor 3 is zero.
- the estimation unit 73 calculates the DC voltage value Vdc_est on the basis of the detection value (the current value I) of the load current flowing between the inverter 13 and the electric motor 3 when braking the electric motor 3 .
- the braking control unit 74 controls the inverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc 0 during a period in which the electric motor 3 is in the regenerative state. Accordingly, it is possible to brake the electric motor 3 more quickly.
- the braking control unit 74 brakes the electric motor 3 by detecting the stop instruction of the inverter 13 from the host device using the above-described control, and controls the inverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc 0 during the braking operation. Accordingly, it is possible to suppress the overvoltage state due to the braking control.
- the braking control unit 74 can interrupt the power flowing from the AC power supply 2 via the diode converter 12 by opening the circuit breaker 4 at a desired timing associated with the braking control of the electric motor 3 . Accordingly, for example, when the circuit breaker 4 is opened during a period in which the electric motor 3 is in the regenerative state, the DC voltage value Vdc_est can be controlled not to exceed the reference voltage Vdc 0 .
- the estimation unit 73 may detect that the electric motor 3 is in the regenerative state, on the basis of the current value I detected by the current sensor AM. In that case, the estimation unit 73 can detect the inflow of regenerative energy from the electric motor 3 to the inverter 13 by detecting the inflow of active power from the electric motor 3 on the basis of the current value I detected by the current sensor AM.
- the braking control unit 74 may control a change in the DC voltage Vdc on the basis of the DC voltage value Vdc_est calculated by the estimation unit 73 .
- the braking control unit 74 controls the inverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc 0 .
- the braking control unit 74 may control the inverter 13 so that more AC power is supplied from the electric motor 3 to the inverter 13 in a range in which the DC voltage value Vdc_est does not exceed the reference voltage Vdc 0 on the DC side. Accordingly, it is possible to brake the electric motor 3 more quickly while suppressing the overvoltage of the DC voltage Vdc.
- a sensor collecting data for calculating the DC voltage value Vdc_est may be at least two current sensors AM.
- a cell unit 6 VI shown in FIG. 4 is different from the cell unit 6 shown in FIG. 2 as below.
- the cell unit 6 VI further includes resistors 15 P and 16 P and switches 15 S and 16 S.
- the resistors 15 P and 16 P and the switches 15 S and 16 S are connected in series with each other. Both ends of the resistors 15 P and 16 P and the switches 15 S and 16 S connected in series with each other are connected in parallel with the smoothing capacitor 14 .
- the switch 15 S, the resistors 15 P and 16 P, and the switch 16 S are connected in series in this order, one end of each of the switches 15 S and 16 S becomes both ends of the resistors 15 P and 16 P and the switches 15 S and 16 S connected in series with each other.
- the connection point of the resistors 15 P and 16 P is connected to the frame of the cell unit 6 VI together with the connection point of the resistors 15 and 16 .
- the cell unit control unit CUC generates a signal for controlling the switching element 13 S constituting the diode converter 12 and the inverter 13 on the basis of the gate pulse signal from the control device 7 . Further, the cell unit control unit CUC generates a signal for controlling the switches 15 S and 16 S on the basis of the control signal from the control device 7 .
- the braking control unit 74 controls the switches 15 S and 16 S in addition to the control of the circuit breaker 4 and the inverter 13 .
- the braking control unit 74 may control the switches 15 S and 16 S in accordance with the timing of controlling the circuit breaker 4 .
- the braking control unit 74 may turn on the switches 15 S and 16 S when turning off the circuit breaker 4 and may turn off the switches 15 S and 16 S when turning on the circuit breaker 4 .
- the switches 15 S and 16 S are normally controlled in an off state by the braking control unit 74 and the resistors 15 P and 16 P are not loads of the diode converter 12 .
- the switches 15 S and 16 S are controlled to be turned on by the braking control unit 74 when the regenerative state of the electric motor 3 is detected. Accordingly, the switches 15 S and 16 S discharge the electric charge accumulated in the smoothing capacitor 14 via the resistors 15 P and 16 P.
- the resistance value R of formulas (1) and (2) is a value when the combined resistance value R1 of the resistors 15 and 16 and the combined resistance value R2 of the resistors 15 and 16 are connected in parallel as shown in the following formula (3).
- the power converter 1 includes the diode converter 12 , the inverter 13 , the smoothing capacitor 14 , the resistors 15 and 16 , the current sensor AM, the estimation unit 73 , and the braking control unit 74 .
- the diode converter 12 rectifies the alternating current from the AC power supply 2 .
- the inverter 13 is formed such that the DC side is connected to the DC output of the diode converter 12 and the AC side is connected to the load L and includes the switching element 13 S which converts the DC power on the DC side into the AC power and the reverse connection diode 13 D which is connected in antiparallel with the switching element 13 S.
- the smoothing capacitor 14 is provided in the DC output of the diode converter 12 .
- the resistors 15 and 16 are connected in parallel with the smoothing capacitor 14 .
- the current sensor AM detects the load current flowing between the inverter 13 and the electric motor 3 .
- the estimation unit 73 calculates the DC voltage value Vdc_est on the basis of the current value I detected by the current sensor AM.
- the braking control unit 74 controls the inverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc 0 during a period in which the electric motor 3 is in the regenerative state. Accordingly, the power converter 1 can brake the electric motor 3 more quickly.
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- Control Of Ac Motors In General (AREA)
Abstract
Description
- The present invention relates to a power converter and an electric motor braking method.
- A power converter supplies AC power converted from DC power to an electric motor and drives an electric motor and a mechanical load interlocked with the rotation of the electric motor. When the electric motor and the mechanical load are braked in a rotation state, regenerative energy is generated by an electromotive force. When the regenerative energy flows from the electric motor to the power converter, a voltage on a DC side (a DC voltage) of the power converter increases. In that case, it may be difficult to quickly stop the electric motor when a discharge circuit is used to avoid the occurrence of an overvoltage state of the DC voltage.
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- Japanese Unexamined Patent Application, First Publication No. Hei 09-255246
- An object of the present invention is to provide a power converter and an electric motor braking method capable of braking an electric motor more quickly.
- A power converter according to an aspect of an embodiment includes: a diode converter; an inverter; a smoothing capacitor; a resistor; a current sensor; an estimation unit; and a control unit. The diode converter rectifies an alternating current from a power supply. The inverter is formed such that a DC side is connected to a DC output of the diode converter and an AC side is connected to an electric motor and includes a semiconductor switching element which converts DC power on the DC side into AC power and a reverse connection diode which is connected in antiparallel with the semiconductor switching element. The smoothing capacitor is provided in the DC output of the diode converter. The resistor is connected in parallel with the smoothing capacitor. The current sensor detects a load current flowing between the inverter and the electric motor. The estimation unit calculates an estimation value of the DC voltage Vdc on the DC side on the basis of a current value I detected by the current sensor. The control unit controls the inverter so that the estimation value of the DC voltage Vdc on the DC side does not exceed a predetermined reference voltage during a period in which the electric motor is in a regenerative state.
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FIG. 1 is a diagram showing an example of a power converter according to a first embodiment. -
FIG. 2 is a diagram showing a cell unit of an embodiment. -
FIG. 3 is a flowchart of a process relating to braking control of an embodiment. -
FIG. 4 is a diagram showing a cell unit according to a second embodiment. - Hereinafter, a power converter of an embodiment will be described with reference to the drawings. Additionally, in the following description, the same reference numerals are given to the components having the same or similar functions. Further, redundant description of the components may be omitted. Furthermore, in the drawings referred to below, control gate wirings and the like may be omitted for convenience of description.
- Here, a “positive electrode P” and a “negative electrode N” are defined first. “Positive electrode P” means a portion having a positive potential when a
power converter 1 is operated. “Negative electrode N” means a portion having a negative potential when thepower converter 1 is operated. - Additionally, a reference voltage Vdc0 of a DC link in the
power converter 1 is defined as a predetermined voltage. The reference voltage Vdc0 is, for example, a voltage between the positive electrode P and the negative electrode N. The reference voltage Vdc0 is sometimes called a DC (DC link) rated voltage. - Referring to
FIGS. 1 to 3 , thepower converter 1 of the embodiment will be described. - The
power converter 1 converts AC power supplied from an AC power supply 2 into DC power, converts the converted DC power into AC power having a desired frequency and voltage, and supplies the AC power to anelectric motor 3. Theelectric motor 3 is, for example, a three-phase induction motor, but is not limited thereto. - The power supply side of the
power converter 1 is connected to the AC power supply 2 via a circuit breaker 4. The circuit breaker 4 interrupts the power supplied from the AC power supply 2 (the power supply) on the basis of the control of a control device 7 to be described later. Additionally, as shown inFIG. 1 , the circuit breaker 4 may be separated from thepower converter 1 or may be a part of thepower converter 1. - In this embodiment, an example in which the
power converter 1 includes a plurality ofcell units 6 s will be described. Additionally, thepower converter 1 may include a three-phase converter and a three-phase inverter instead of the plurality ofcell units 6 s. - First, the overall electrical configuration of the
power converter 1 will be described.FIG. 1 is a diagram showing an example of thepower converter 1 of the embodiment. InFIG. 1 , an electric circuit system is indicated by a single line and switches and the like are not shown. Thepower converter 1 includes, for example, an input transformer 5, a plurality ofcell units 6 s, a control device 7, and a current sensor AM. - The AC power is supplied from the AC power supply 2 to the input transformer 5. The input transformer 5 transforms the voltage of the AC power supplied from the AC power supply 2 (primary voltage) into a desired secondary voltage and supplies the AC power of the secondary voltage to each of the plurality of
cell units 6 s. The input transformer 5 includes a primary coil and a plurality of groups of coils (secondary coils) insulated from each other. The primary coil and the secondary coil are also insulated. - The plurality of
cell units 6 s include, for example, three first-phase load cell units 6A1, 6A2, and 6A3 (U1, U2, and U3 in the drawings), three second-phase load cell units 6B1, 6B2, and 6B3 (V1, V2, and V3 in the drawings), and three third-phase load cell units 6C1, 6C2, and 6C3 (W1, W2, and W3 in the drawings). The cell units 6A1, 6A2, 6A3, 6B1, 6B2, 6B3, 6C1, 6C2, and 6C3 have the same circuit configuration and will be simply referred to as the cell unit 6 when they are described without distinction. Each cell unit 6 converts the three-phase AC power supplied from the secondary coil of the input transformer 5 into DC power, converts the converted DC power into AC power having a desired frequency and voltage, and outputs the AC power. - For example, a first group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6A1. A second group of the secondary side of the input transformer 5 is connected to the input of the cell unit V1. A third group of the secondary side of the input transformer 5 is connected to the input of the cell unit W1. A fourth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6A2. A fifth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6B2. A sixth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6C2. A seventh group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6A3. An eighth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6B3. A ninth group of the secondary side of the input transformer 5 is connected to the input of the cell unit 6C3.
- In this embodiment, the outputs of the cell units 6A1, 6A2, and 6A3 are electrically connected in series in the shown order. An output terminal of the cell unit 6A3 which is not connected to the cell unit 6A2 is connected to the first phase (U phase) of the
electric motor 3. An output terminal of the cell unit 6A1 which is not connected to the cell unit 6A2 is connected to a neutral point. In this embodiment, the outputs of the cell units 6B1, 6B2, and 6B3 are electrically connected in series in the shown order. An output terminal of the cell unit 6B3 which is not connected to the cell unit 6B2 is connected to the second phase (V phase) of theelectric motor 3. An output terminal of the cell unit 6B1 which is not connected to the cell unit 6B2 is connected to a neutral point. In this embodiment, the outputs of the cell units 6C1, 6B2, and 6B3 are electrically connected in series in the shown order. An output terminal of the cell unit 6C3 which is not connected to the cell unit 6C2 is connected to the third phase (W phase) of theelectric motor 3. An output terminal of the cell unit 6C1 which is not connected to the cell unit 6C2 is connected to a neutral point. Accordingly, thepower converter 1 can supply a large amount of AC power to theelectric motor 3. - A current sensor AM1 and a current sensor AM2 detect a load current (a phase current) flowing between the
electric motor 3 and the inverter 13 (FIG. 2 ) of thepower converter 1. For example, the current sensor AM1 is provided on the first phase of the AC output and the current sensor AM2 is provided on the third phase of the AC power. Since the second-phase current of the AC output can be obtained from the values of the current sensor AM1 and the current sensor AM2, the second-phase current can be omitted. Additionally, when the current sensor AM1 and the current sensor AM2 are not distinguished from each other, they may be simply referred to as a current sensor AM. A current value detected by the current sensor AM may be referred to as a current I. - The control device 7 controls or protects each cell unit 6. The control device 7 includes, for example, a
storage unit 71, anoperation control unit 72, anestimation unit 73, and abraking control unit 74. - The
storage unit 71 stores a variety of data relating to the control of the plurality ofcell units 6 s. The variety of data includes, for example, a limit value (a threshold value Vth) for limiting the overvoltage of the DC voltage of the cell unit 6, a reference voltage Vdc0 of the DC voltage of the cell unit 6, history data and integrated value data of a current value I detected by the current sensor AM, an estimation value of a DC voltage value Vdc of the cell unit 6 (hereinafter, referred to as a DC voltage value Vdc_est), and the like. The threshold value Vth is defined as, for example, the upper-limit value of the DC voltage of the DC link. The reference voltage Vdc0 is an example of the control target voltage. - The
operation control unit 72 generates a control signal for controlling a switching element 13S (FIG. 2 ) included in each cell unit 6 on the basis of data stored in thestorage unit 71, for example, information representing the DC voltage value Vdc_est and information representing the current I detected by the current sensor AM. Theoperation control unit 72 controls each cell unit 6 by sending the generated control signal to each cell unit 6. Theoperation control unit 72 acquires a signal representing the control state of the electric motor 3 (for example, a feedback signal of a rotation speed) and controls each cell unit 6 on the basis of the feedback signal. Further, the control device 7 acquires a control instruction signal of theelectric motor 3 from other devices and controls each cell unit 6 on the basis of the control instruction signal. - The
estimation unit 73 calculates the DC voltage value Vdc_est on the basis of the current value I detected by the current sensor AM. The calculation of the DC voltage value Vdc_est will be described below. - The
braking control unit 74 controls each unit to brake theelectric motor 3 while adjusting the DC voltage Vdc not to exceed the reference voltage Vdc0 on the basis of the DC voltage value Vdc_est. For example, thebraking control unit 74 opens the circuit breaker 4 at a desired timing associated with the braking control of theelectric motor 3. This desired timing may be matched when theelectric motor 3 is in the regenerative state. - Further, the
braking control unit 74 controls theinverter 13 so that more AC power is supplied from theelectric motor 3 to theinverter 13 during a period in which theelectric motor 3 is in the regenerative state. At that time, thebraking control unit 74 adjusts the DC voltage value Vdc_est not to exceed the reference voltage Vdc0 on the DC side. The control of the circuit breaker 4 and theinverter 13 will be described in detail later. - Next, the cell unit 6 will be described.
-
FIG. 2 is a diagram showing the cell unit 6 of the embodiment. The cell unit 6 includes, for example, adiode converter 12, aninverter 13, a smoothingcapacitor 14,resistors diode converter 12 and the DC input of theinverter 13 are electrically connected with each other via a DC link between the positive electrodes (P) and between the negative electrodes (N). The smoothingcapacitor 14 is provided in the DC link and the terminal of the smoothingcapacitor 14 is electrically connected to the positive electrode and the negative electrode of the DC link. - In the following description, the cell unit 6A1 will be illustrated and an example thereof will be described while showing the connection relationship with the outside. The same applies to the other cell units 6.
- The
diode converter 12 is a three-phase AC input type forward converter and the input portion is electrically connected to one group of the secondary side of the input transformer 5. Thediode converter 12 converts the AC power input from the input transformer 5 into the DC power by rectifying the alternating current. The smoothingcapacitor 14 smoothes the converted DC voltage. - The
inverter 13 is a single-phase AC output type inverse converter. Theinverter 13 includes, for example, the switching element 13S which converts the DC power on the DC side into the AC power and a reverse connection diode 13D which is connected in antiparallel with the switching element 13S. The switching element 13S is an example of the semiconductor switching element. In theinverter 13, the DC side is connected to the DC output of thediode converter 12 and the AC side is connected in series with the output of theelectric motor 3 or another cell unit 6. Theinverter 13 outputs, for example, the converted AC power to the first phase of theelectric motor 3. - The
resistors capacitor 14. The connection point of theresistors resistors capacitor 14. - The cell unit control unit CUC generates a signal for controlling a switching element constituting the
diode converter 12 and theinverter 13 on the basis of a gate pulse signal from the control device 7. The gate pulse signal from the control device 7 is given to the switching element constituting thediode converter 12 and theinverter 13 via the cell unit control unit CUC. -
FIG. 3 is a flowchart of a process associated with the braking control of the embodiment. - For example, the initial value of the DC voltage value Vdc_est is defined as 0. A series of processes shown in the drawing is repeatedly performed at predetermined intervals.
- First, the
braking control unit 74 determines whether or not the DC voltage value Vdc_est exceeds the threshold value Vth (step SA02). Additionally, the DC voltage value Vdc_est is calculated in the previous process cycle. - When the DC voltage value Vdc_est exceeds the threshold value Vth, the
braking control unit 74 turns off the circuit breaker 4 (step SA04) and ends a series of processes in the current cycle. - When the DC voltage value Vdc_est does not exceed the threshold value Vth, the
braking control unit 74 operates theinverter 13 without turning off the circuit breaker 4 (step SA06). - Next, the
braking control unit 74 determines whether or not the stop instruction of theinverter 13 from the host device is detected (step SA08). When the stop instruction of theinverter 13 from the host device is not detected, thebraking control unit 74 advances the process to step SA02. - When the stop instruction of the
inverter 13 from the host device is detected, thebraking control unit 74 stops the output of the inverter 13 (step SA10). Next, thebraking control unit 74 turns off the circuit breaker 4 (step SA12). - Next, the
estimation unit 73 calculates the DC voltage value Vdc_est using the following formula (1) (step SA20). For example, the DC voltage value Vdc_est is defined by the following formula (1). -
- The variables in formula (1) are as follows.
- Vdc0: Reference voltage of DC part
- R: Resistance value of DC part
- C: Capacitor of DC part
- t: Time
- Ir(t): Regenerative current flowing from
electric motor 3 toinverter 13 at time t - In the case of the cell unit 6 of the embodiment, the resistance value becomes the sum of the resistance values of the
resistor 15 and theresistor 16. The capacitor C becomes the capacity of the smoothingcapacitor 14. Additionally, when the smoothingcapacitor 14 is configured as a combination of capacitors connected in parallel with each other, the capacitor C becomes the sum of the capacities of the plurality of capacitors. - The first term on the right side of the above-described formula (1) sets the reference voltage Vcd0 of the DC part as the initial value and defines a discharge characteristic according to a time constant RC defined by the resistance value R of the DC part and the capacitor C of the DC part. The second term defines a change in voltage due to the charging of the capacitor C of the DC part charged by the regenerative current Ir(t). By adding the first term and the second term, the voltage applied to the capacitor C, that is, the terminal voltage of the smoothing capacitor 14 (the DC voltage of the DC link) is derived.
- When the terminal voltage of the smoothing
capacitor 14 can be controlled to be lower than the reference voltage Vcd0 of the DC part, an overvoltage does not occur in the DC part. That is, the occurrence of the overvoltage can be suppressed by adjusting the regenerative current Ir(t) to satisfy the following formula (2). -
- As described above, the right side of formula (2) is the same as the right side of formula (1). Here, the
braking control unit 74 determines whether or not the DC voltage value Vdc_est derived by the calculation using formula (1) exceeds the predetermined reference voltage Vdc0 of the DC part (step SA22). This determination corresponds to the determination of whether the condition of formula (2) is satisfied. Accordingly, thebraking control unit 74 can indirectly detect the charging state of the smoothingcapacitor 14. Additionally, the integration of the regenerative current Ir(t) may be calculated by using the integrated value of Ir(t) for a predetermined period. For example, the predetermined period may be set to a range that is a natural number multiple of the basic cycle of the AC output of theinverter 13. - When the DC voltage value Vdc_est does not exceed the reference voltage Vdc0 of the DC part, the
braking control unit 74 controls the regenerative current from theelectric motor 3 to increase by increasing the instruction value of the inverter 13 (step SA24). Accordingly, thebraking control unit 74 can allow more current to flow from the side of theelectric motor 3 to theinverter 13 by increasing the DC voltage value Vdc estimated to have a margin until the overvoltage state not to exceed the reference voltage Vdc0. Additionally, it is conceived that the instruction value of theinverter 13 is to define the regeneration amount and the regeneration amount increases in accordance with an increase in the instruction value. - When the DC voltage value Vdc_est exceeds the set value (the threshold value) Vdc0, the
braking control unit 74 controls the regenerative current from theelectric motor 3 to decrease by decreasing the instruction value of the inverter 13 (step SA26). Accordingly, thebraking control unit 74 can decrease the current flowing from the side of theelectric motor 3 to theinverter 13 to decrease the DC voltage value Vdc estimated to be in the overvoltage state. - When the process of SA24 or SA26 ends, the
braking control unit 74 determines whether the speed of theelectric motor 3 is zero (step SA28). Thebraking control unit 74 repeats the process from step SA20 when the speed of theelectric motor 3 is not zero. Thebraking control unit 74 ends a series of processes of the current cycle when the speed of theelectric motor 3 is zero. Additionally, the speed of theelectric motor 3 when the speed becomes lower than the speed defined by the threshold value may be regarded as zero by determining the speed of theelectric motor 3 using the threshold value in the vicinity of zero instead of determining whether or not the speed of theelectric motor 3 is zero. - According to the above-described embodiment, the
estimation unit 73 calculates the DC voltage value Vdc_est on the basis of the detection value (the current value I) of the load current flowing between theinverter 13 and theelectric motor 3 when braking theelectric motor 3. Thebraking control unit 74 controls theinverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc0 during a period in which theelectric motor 3 is in the regenerative state. Accordingly, it is possible to brake theelectric motor 3 more quickly. - The
braking control unit 74 brakes theelectric motor 3 by detecting the stop instruction of theinverter 13 from the host device using the above-described control, and controls theinverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc0 during the braking operation. Accordingly, it is possible to suppress the overvoltage state due to the braking control. - The
braking control unit 74 can interrupt the power flowing from the AC power supply 2 via thediode converter 12 by opening the circuit breaker 4 at a desired timing associated with the braking control of theelectric motor 3. Accordingly, for example, when the circuit breaker 4 is opened during a period in which theelectric motor 3 is in the regenerative state, the DC voltage value Vdc_est can be controlled not to exceed the reference voltage Vdc0. - Additionally, the
estimation unit 73 may detect that theelectric motor 3 is in the regenerative state, on the basis of the current value I detected by the current sensor AM. In that case, theestimation unit 73 can detect the inflow of regenerative energy from theelectric motor 3 to theinverter 13 by detecting the inflow of active power from theelectric motor 3 on the basis of the current value I detected by the current sensor AM. - The
braking control unit 74 may control a change in the DC voltage Vdc on the basis of the DC voltage value Vdc_est calculated by theestimation unit 73. In this case, thebraking control unit 74 controls theinverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc0. At that time, thebraking control unit 74 may control theinverter 13 so that more AC power is supplied from theelectric motor 3 to theinverter 13 in a range in which the DC voltage value Vdc_est does not exceed the reference voltage Vdc0 on the DC side. Accordingly, it is possible to brake theelectric motor 3 more quickly while suppressing the overvoltage of the DC voltage Vdc. - In the above-described embodiment, since the DC voltage value Vdc_est can be calculated on the basis of the above-described formula (1) without providing a voltage detector for detecting the DC voltage Vdc on the DC side for each cell unit 6, the configuration of the
power converter 1 can be simplified. For example, a sensor collecting data for calculating the DC voltage value Vdc_est may be at least two current sensors AM. - Referring to
FIGS. 1 to 4 , a second embodiment will be described. In the first embodiment, an example in which theresistors - A cell unit 6VI shown in
FIG. 4 is different from the cell unit 6 shown inFIG. 2 as below. The cell unit 6VI further includes resistors 15P and 16P and switches 15S and 16S. - The resistors 15P and 16P and the switches 15S and 16S are connected in series with each other. Both ends of the resistors 15P and 16P and the switches 15S and 16S connected in series with each other are connected in parallel with the smoothing
capacitor 14. For example, when the switch 15S, the resistors 15P and 16P, and the switch 16S are connected in series in this order, one end of each of the switches 15S and 16S becomes both ends of the resistors 15P and 16P and the switches 15S and 16S connected in series with each other. In this case, the connection point of the resistors 15P and 16P is connected to the frame of the cell unit 6VI together with the connection point of theresistors - The cell unit control unit CUC generates a signal for controlling the switching element 13S constituting the
diode converter 12 and theinverter 13 on the basis of the gate pulse signal from the control device 7. Further, the cell unit control unit CUC generates a signal for controlling the switches 15S and 16S on the basis of the control signal from the control device 7. - Additionally, the
braking control unit 74 controls the switches 15S and 16S in addition to the control of the circuit breaker 4 and theinverter 13. Thebraking control unit 74 may control the switches 15S and 16S in accordance with the timing of controlling the circuit breaker 4. For example, thebraking control unit 74 may turn on the switches 15S and 16S when turning off the circuit breaker 4 and may turn off the switches 15S and 16S when turning on the circuit breaker 4. - For example, the switches 15S and 16S are normally controlled in an off state by the
braking control unit 74 and the resistors 15P and 16P are not loads of thediode converter 12. The switches 15S and 16S are controlled to be turned on by thebraking control unit 74 when the regenerative state of theelectric motor 3 is detected. Accordingly, the switches 15S and 16S discharge the electric charge accumulated in the smoothingcapacitor 14 via the resistors 15P and 16P. - According to the above-described control, the discharge amount in the regenerative state increases. Specifically, the resistance value R of formulas (1) and (2) is a value when the combined resistance value R1 of the
resistors resistors -
R=R1×R2/(R1+R2) (3) - According to the above-described embodiment, since it is possible to increase the power loss amount in the regenerative state in addition to the same effect as the first embodiment, it is possible to more efficiently discharge the electric charge accumulated in the smoothing
capacitor 14. - According to at least one of the above-described embodiments, the
power converter 1 includes thediode converter 12, theinverter 13, the smoothingcapacitor 14, theresistors estimation unit 73, and thebraking control unit 74. Thediode converter 12 rectifies the alternating current from the AC power supply 2. Theinverter 13 is formed such that the DC side is connected to the DC output of thediode converter 12 and the AC side is connected to the load L and includes the switching element 13S which converts the DC power on the DC side into the AC power and the reverse connection diode 13D which is connected in antiparallel with the switching element 13S. The smoothingcapacitor 14 is provided in the DC output of thediode converter 12. Theresistors capacitor 14. The current sensor AM detects the load current flowing between theinverter 13 and theelectric motor 3. Theestimation unit 73 calculates the DC voltage value Vdc_est on the basis of the current value I detected by the current sensor AM. Thebraking control unit 74 controls theinverter 13 so that the DC voltage value Vdc_est does not exceed the reference voltage Vdc0 during a period in which theelectric motor 3 is in the regenerative state. Accordingly, thepower converter 1 can brake theelectric motor 3 more quickly. - Although some embodiments of the present invention have been described, these embodiments are presented as examples and are not intended to limit the scope of the present invention. These embodiments can be implemented in various other forms and various omissions, replacements, and changes can be made without departing from the spirit of the present invention. These embodiments and their modifications are included in the present invention described in the claims and the equivalents thereof when they are included in the scope and the gist of the present invention.
-
-
- 1 Power converter
- 2 AC power supply
- 3 Electric motor
- 4 Circuit breaker
- 5 Input transformer
- 6 Cell unit
- 6 s Cell units
- 7 Control device
- 12 Diode converter
- 13 Inverter
- 13S Switching element
- 13D Reverse connection diode
- 14 Smoothing capacitor
- 15, 15P, 16, 16P Resistor
- 15S, 16S Switch
- CUC Cell unit control unit
- 71 Storage unit
- 72 Operation control unit
- 73 Estimation unit
- 74 Braking control unit
- AM, AM1, AM2 Current sensor
Claims (7)
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PCT/JP2019/023697 WO2020250429A1 (en) | 2019-06-14 | 2019-06-14 | Power conversion device and electric motor braking method |
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US20220321021A1 true US20220321021A1 (en) | 2022-10-06 |
US11949341B2 US11949341B2 (en) | 2024-04-02 |
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US17/310,302 Active 2040-05-14 US11949341B2 (en) | 2019-06-14 | 2019-06-14 | Power converter and electric motor braking method |
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US (1) | US11949341B2 (en) |
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US8120294B2 (en) * | 2008-03-10 | 2012-02-21 | Hitachi Industrial Equipment Systems Co., Ltd. | Power transducer |
US8305018B2 (en) * | 2009-02-09 | 2012-11-06 | Toyota Jidosha Kabushiki Kaisha | Power supply system and electric powered vehicle using the same |
US10236805B2 (en) * | 2013-01-24 | 2019-03-19 | Regal Beloit America, Inc. | Methods and systems for controlling an electric motor |
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JPH0819266A (en) | 1994-06-30 | 1996-01-19 | Shimadzu Corp | Inverter |
JPH09255246A (en) | 1996-03-19 | 1997-09-30 | Mitsubishi Electric Corp | Regenerative electric power control device |
JP2002171695A (en) | 2000-12-06 | 2002-06-14 | Meidensha Corp | Motor drive system |
JP3773794B2 (en) | 2001-01-31 | 2006-05-10 | 東芝三菱電機産業システム株式会社 | Power converter |
JP4634817B2 (en) * | 2005-02-22 | 2011-02-16 | 株式会社Ihi | Load drive device |
JP4538359B2 (en) | 2005-03-31 | 2010-09-08 | 株式会社日立産機システム | Electrical circuit module |
JP5511515B2 (en) | 2010-05-31 | 2014-06-04 | 株式会社日立製作所 | Power converter |
JP5205420B2 (en) | 2010-06-25 | 2013-06-05 | 株式会社日立製作所 | Electric motor system, power converter, and method for controlling power converter |
JP5829412B2 (en) | 2011-03-25 | 2015-12-09 | 東芝シュネデール・インバータ株式会社 | Inverter device and smoothing capacitor capacity estimation method |
JP5910155B2 (en) * | 2012-02-22 | 2016-04-27 | 株式会社明電舎 | Voltage control device for power converter |
JP5932136B2 (en) | 2013-03-12 | 2016-06-08 | 三菱電機株式会社 | Motor control device |
JP6334367B2 (en) * | 2014-11-07 | 2018-05-30 | 日立オートモティブシステムズ株式会社 | Inverter control device |
-
2019
- 2019-06-14 WO PCT/JP2019/023697 patent/WO2020250429A1/en active Application Filing
- 2019-06-14 JP JP2020549711A patent/JP7004838B2/en active Active
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US8120294B2 (en) * | 2008-03-10 | 2012-02-21 | Hitachi Industrial Equipment Systems Co., Ltd. | Power transducer |
US8305018B2 (en) * | 2009-02-09 | 2012-11-06 | Toyota Jidosha Kabushiki Kaisha | Power supply system and electric powered vehicle using the same |
US10236805B2 (en) * | 2013-01-24 | 2019-03-19 | Regal Beloit America, Inc. | Methods and systems for controlling an electric motor |
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WO2020250429A1 (en) | 2020-12-17 |
CN112470388A (en) | 2021-03-09 |
JP7004838B2 (en) | 2022-01-21 |
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CN112470388B (en) | 2023-09-01 |
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